In recent years, a light measurement method using light with a predetermined wavelength such as near-infrared light has been used for a noninvasive living body measurement such as a breast measurement of breast cancer examination (for example, see Patent Documents 1, 2). In the light measurement method, measurement light of a predetermined wavelength is input through a light input unit into a measurement object region of a subject. Then, the output light propagated inside the measurement object region and output to the outside through a light output unit is detected, and according to the detection result, internal information of the measurement object region is acquired.
In the light measurement method, for example, a hemoglobin amount (oxygenated hemoglobin amount HbO2, deoxygenated hemoglobin amount Hb, or total hemoglobin amount tHb) in the measurement object region can be acquired as the internal information of the measurement object region. For example, Non Patent Document 1 discloses a method of acquiring a hemoglobin amount by a near-infrared spectroscopic measurement and evaluating a property of a tumor based on the acquired hemoglobin amount.